Some of conventional vehicular illumination devices include a long light guiding lens.
In general, this type of illumination device can include a light emitting diode as a light source and a light guiding lens has an end face to which the light emitting diode faces. The light emitted from the light emitting diode can enter the light guiding lens through the end face to illuminate the light guiding lens with the light. Japanese Patent Application Laid-Open No. 2013-235775 discloses this type illumination device.
By the way, the illumination devices in recent years have parts layout within the device the usable area of which is limited due to the miniaturization and multifunctionality as well as the requirement in heat dissipation measures accompanying with the high optical output of the light source. In order to dispose the light source suitable for such an illumination device with a long bent light guiding lens, it is necessary to bend the long light guiding lens at a position near the light source.
In this case, the bend portion of the light guiding lens should be formed at a curved area or corner area in order not to prevent the light from being guided therethrough. However, if the light emitted from the light source and entering the light guiding lens is random light uncontrolled, part of the light may be incident on an inner face of the bend portion on the outer side at an angle less than the critical angle, resulting in leakage of light to the outside of the light guiding lens through that portion.
Even when the light emitted from the light source and entering the light guiding lens is parallel light along the portion of the light guiding lens up to the bend portion, if the bend portion is formed by being bent by a sharp angle, part of the light may still be incident on an inner face of the bend portion on the outer side at an angle less than the critical angle, resulting in leakage of light to the outside of the light guiding lens.